Chapter 1
Atoms, Elements, Compounds, and Molecules

Guided Inquiry Activities (Web): 1, Elements, Compounds, and Molecules; 2, Bonding; 3, Mixtures and States of Matter; 4, Water; 8, pH

Learning Objectives

1. Name and describe the particles that make up an atom.
2. Describe the relationship of atoms and elements to the periodic table.
3. Define and recognize ions: cations and anions.
4. Recognize and identify ionic bonds and covalent bonds.
5. Recognize and distinguish between ionic compounds and covalent molecules.
6. Describe what holds ionic compounds together and how that is different from what holds covalent molecules together.
7. Describe the types of attractions that occur between compounds and molecules: electrostatic, hydrogen bonding, and hydrophobic attractions, and be able to identify examples of these interactions.
8. Describe the intramolecular and intermolecular bonds that make up water, and be able to explain the intermolecular forces that cause freezing, melting, and vaporization of water.
9. Describe what makes something acidic, and what molecules are acids.

1.1 Introduction

The process of cooking, baking, and preparing food is essentially an applied science. Anthropologists and historians venture that cooking originated when a pen holding pigs or other livestock caught fire or a piece of the day's catch of mammoth fell into the fire pit. The smell of roasted meat must have enticed early people to "try it"; the curious consumers found culinary and nutritional benefits to this discovery. The molecular changes that occurred during cooking made the meat more digestible and the protein and carbohydrates more readily available as nutrients. Contaminating microbes were eliminated during cooking, which made the consumers more healthy and able to survive. Moreover, the food was tastier due to the heat-induced chemical reactions between the oxygen in the air and the fat, proteins, and sugar in the meat. Harnessing the knowledge of what is happening to our food at the molecular level is something that good scientists and chefs use to create new appetizing food and cooking techniques.

We are all born curious. Science and cooking are natural partners where curiosity and experimentation can lead to exhilarating and tasty new inventions. Scientific discovery is driven by hypothesis (see Figure 1.1 for a model of the scientific method). An observation of an event creates a question and/or a statement that explains the observation or phenomenon: the hypothesis. The hypothesis can then be tested by a series of experiments and controls that supports or falsifies the hypothesis, starting the cycle over again. For example, a scientist might observe that the growth rate of cancer cells in a petri dish slows when the cells are exposed to a sea sponge. The scientist may then hypothesize that a molecule found in the sponge binds to a protein in cancer cells. After adding the compound to a tumor, its growth slows and the cells die. Looking at how all of the individual molecules found in the sea sponge affect the growth of cancer cells can test this hypothesis. These experiments can lead to a more advanced hypothesis, testing, and eventually finding a new compound that can be used to fight cancer.

Figure 1.1 The scientific method. Scientists use a testable method originating from observations to generate a testable hypothesis to conduct their work. A cook or baker can also use this method to create more interesting food.

Cooking can also be a hypothesis-driven process that utilizes biology, chemistry, and physics. As you cook, you use biology, chemistry, and physics to create hypotheses in the kitchen, even if you aren't aware of being a scientist. Each time you try a recipe, you make observations. You may ask yourself questions about what you added to the concoction or how the food was baked or cooked. This creates a hypothesis or a statement/prediction that you can test through experimentation (your next attempt at the dish). A nonscientific idea is often approached as something to prove. That is different from hypothesis testing. A hypothesis is falsified rather than proven by testing. Cooking does just this; it will falsify your test rather than prove it. Tasting, smelling, and visualizing your results tell you if your hypothesis was supported or falsified. If wrong, you may create a new hypothesis that might be generated by the time you have washed the dishes from your first experiment. Learning more of the basic science behind food and cooking will help you appreciate the world around you and become a better scientist and a better cook, baker, and consumer.

1.2 Fundamentals of Food and Cooking

Bread baking provides a great example of the importance of having a scientific understanding of cooking and baking. Take a close look at bread. Notice that it is made of large and small caves surrounded by a solid wall (Figure 1.2).

Figure 1.2 Structure of bread. A close look at bread demonstrates the requirement of proteins and carbohydrates needed to trap expanding gases.

gmeviphoto/Adobe Stock Photos

The key to bread is making a way to trap expanding gases in the dough. Adding water to flour and sugar allows for the hydration and mixing of proteins and carbohydrates. Kneading the dough stretches a protein network called gluten, which allows for an interconnected network of protein ready to trap gas that is generated by the yeast. During the proofing step of making bread, the yeast converts sugar into energy-filled molecules, ethanol, carbon dioxide gas, and other flavorful by-products. The heat applied during baking allows the water to escape as steam, which expands the bread, links the gluten protein molecules further, and traps carbon dioxide gas. While this is happening, the heat catalyzes chemical reactions between proteins and sugars, creating a beautiful brown color, a dense texture, and over 500 new aromatic compounds that waft to your nose. Clearly, there is a lot of science that goes into making a loaf of bread.

Preparing food and drink is mostly a process of changing the chemical and physical nature of the food. Molecules react to form new compounds; heat changes the nature of how food molecules function and interact with each other, and physical change brings about new textures and flavors to what we eat. To gain a better appreciation for these chemical and physical processes, a fundamental understanding of the building blocks of food and cooking must first be understood. In the following chapter, we will study the biological macromolecules that make up the protein, carbohydrates, and fat in our diets.

One of the most important building blocks of food is water; our bodies, food, and environment are dependent on the unique chemistry and biology of this molecule. Large biological molecules such as proteins, carbohydrates, and fats comprise the basic building blocks of food. Smaller molecules, including vitamins, salts, and organic molecules, add important components to cooking and the taste of food. Finally, the basics of plant and animal cells and cellular organization are key to understanding the nature of food and cooking processes. However, before we get into some of the science fundamentals, it is important to recognize and acknowledge the origins of the chefs who first embraced the science behind their profession.

1.2.1 Science, Food, and Cooking

Many chefs and bakers embrace the collaboration of science and food. Historically, one means whereby science has been utilized in the kitchen is in the area of food technology; the discipline in which biology, physical sciences, and engineering are used to study the nature of foods, the causes of their deterioration, and the principles underlying food processing. This area of food science is very important in ensuring the safety and quality of food preparation, processing of raw food into packaged materials, and formulation of stable and edible food. College undergraduates can major in "food science" or attend graduate studies in this area, working for a food production company where they might look at the formulation and packaging of cereals, rice, or canned vegetables. Recently, a new marriage of science and food, coined molecular gastronomy, has grown to influence popular culture that extends far beyond the historical definition of food science. A physicist at Oxford, Dr. Nicholas Kurti's interest in food led him to meld his passion for understanding the nature of matter and cooking. In 1984, Harold McGee, an astronomist with a doctorate in literature from Yale University, wrote the first edition of the influential and comprehensive book On Food and Cooking: The Science and Lore of the Kitchen [1]. This fascinating book is the basis for much of the molecular gastronomy movement and describes the scientific and historical details behind most common (and even uncommon) culinary techniques. Together with cooking instructor Elizabeth Cawdry Thomas, McGee and Kurti held a scientific workshop/meeting to bring together the physical sciences with cooking in 1992 in Erice, Italy. While there were more scientists than chefs attending, with a 5 : 1 ratio, the impact of the meeting was significant. It was at Erice that the beginnings of what was then called molecular and physical gastronomy became the catalyst for an unseen growth in science and cooking. Hervé This, a chemist who studies the atomic and subatomic nature of chemistry, attended the workshop and has been a key player...